This invention relates to a bending beam (transverse beam, cradle), especially for elevated train structures, consisting of at least respectively one structural girder of metal, particularly steel, and a nonmetallic material, especially concrete.
Bending girders, especially bending girders with a high extreme fiber distance (edge-to-axis spacing) and great accuracy requirements, are generally manufactured from steel, resulting in a number of difficulties. Thus, buckling occurs, for example, in thin-walled cross sections under compressive stress which considerably impairs the geometry and accuracy of the cross section, without the strength limit of the material having been exceeded in individual aspects. Furthermore, such steel beams tend to show only insufficiently damped resonance oscillations, because of the large Hooke's range (proportional limit) of certain types of steel when scantily designed (designed with minimum total cross-sectional area). Also, unduly high forces occur at the points of application of the bending forces, since at these points the load is not effective on the entire cross section of the beam. These troublesome phenomena have been counteracted either by designing the entire structural profile very generously, which results in high additional costs due to the price of steel, or by welding or riveting partial reinforcements to the endangered points which, in turn, leads to a significant increase in costs because of the additional work connected therewith.
In part, such steel bending beams act like the resonators of musical instruments with respect to sound vibrations introduced into the beams, which should be avoided for the sake of environmental protection (noise abatement).
By the use of pure steel-concrete beams, the above-mentioned disadvantages can be partially reduced or avoided, as long as the extremely high inherent weight of such a beam does not play a decisive part.
When considering bending beams for elevated trains, a construction of the train support structure in concrete would normally be practicable only in case of favorable ground conditions due to weight. However, at least on soft ground, steel girders must be used which, due to the great extreme fiber distance of about one meter and supporting widths of about 20 meters show a high discrepancy between the wall thicknesses resulting when considering the stresses occurring only in the longitudinal direction of the profile and the wall thicknesses which ensure buckling strength. Taking the entire stresses into account; with a maximally permissible limit of sagging of 2 mm. per supporting width, even a partial, actually otherwise harmless buckling at force application points will result in damage.
It is known from German Pat. No. 701,175 to impart greater tensile strength to iron frames by a coaxial lining with nonmetallic material, in order to save steel and thus expenses in this way. However, this invention cannot be applied to the bending beam since, for weight reasons, the insertion of a concrete pipe into an iron tube brings more disadvantages than advantages. In particular, with the pipe diameters of 1-2 meters necessary for elevated train routes, an internal pipe which is self-supporting and distributes the stresses resulting from the points of force application must have a wall thickness of several centimeters; thus, no appreciable advantage with respect to the weight is achieved over a steel-concrete mode of construction.
It is an object of this invention to provide bending beams, particularly with a high extreme fiber distance, which afford a minimum steel cross section with a low total weight and without partial metal reinforcement, and offer the possibility of the introduction of individual stresses without deformation. Additionally, the bending beam is to attenuate vibrations and sound oscillations introduced therein, and the total costs are to be kept at a minimum.
This object is attained, according to this invention, by providing that the structural girder or girders of metal are reinforced by structural girders of a nonmetallic material at the places under compressive stress and/or under buckling stress, as well as at the force application points of the bending beam. In this construction, the structural girder of a nonmetallic material, especially concrete, supports the cross sections under buckling stress due to compressive forces, to which cross sections, the structural girder is joined by a casting process by means of reinforcing beads pressed into the cross sections. The nonmetallic material absorbs compressive stresses at buckling points and introduces such stresses again into the steel girder after the buckling point, so that nonuniformities in the nonmetallic profile need not be considered, as long as they do not coincide with a buckling point. Furthermore, a continuous profile, for example of concrete, is less expensive than the mounting of local reinforcements of steel at the main buckling points, and even if a buckling point has not been taken into account inadvertently, no damage is done. The nonmetallic structural girder can moreover be arranged as corrosion protection or heat protection on the main weathering and sunlight side, in order to prevent corrosion or buckling by heat. The bending beam of the present invention is furthermore capable of vibrating to only a very damped extent; this does not only attenuate the noise production when the train passes over the route, but the vibrations are likewise reduced which caused by the periodic travel over supporting columns.
Another embodiment of this invention resides in that the structural girder consists of a nonmetallic material made up of series-arranged individual sections. Since the girder does not have a force-transmitting effect in use in its longitudinal direction, it is possible by this feature of the invention to mount the nonmetallic profiles, such as reinforcing plates additionally to the girder only after the assembly of the metallic profile or profiles, for example into an elevated-train foundation. In this connection, profiled plates with mounting elements for the introduction of forces into the train construction can be prefabricated by mass production and fittingly inserted at the construction site by means of cut-to-order spacer elements.
In accordance with another embodiment of the invention, the metallic structural girder is a pipe to which is mounted a structural girder of a nonmetallic cross section on the outside of one or both quadrants which together form the portion of the structural girder cross section facing the bearing loads. In another preferred embodiment of the invention, the cross section of the structural girder forms essentially a right triangle, wherein the bending beam has on its outside a horizontal contact surface and at least one vertical contact surface. In this connection, a pipe which is particularly inexpensive and has been produced by series production can be used, which, on the one hand, absorbs bending loads and, on the other hand, can serve for receiving, in its interior, supply lines, cargo, and the like, wherein the inner side can be lined with one or more metallic or nonmetallic profiles. The other profile, as it is required, for example, for the mounting of elevated-train mechanisms, is applied to the outside of the pipe, for example by cementing, or is poured onto the roughened or corrugated surface of the pipe.
Another embodiment of the invention resides in that the metallic structural girder has horizontal tensile and compressive zones connected with one another by thin-walled, vertical webs, and that at least one of the webs is associated with a profile element of approximately the same height, made of a nonmetallic material, as the reinforcing means. This makes it possible to design such profiles in the web according to minimally permissible tensile and compressive stresses, since the deflected profile member of nonmetallic material prevents a buckling or crushing of the web. Moreover, the nonmetallic profile is suitable for the absorption of compressive stresses; this makes it possible to design the steel chord facing the bending load, representing the compression zone, to be of a lower strength.
According to a further embodiment of this invention, the metallic profile girder forms a closed hollow contour with at least one horizontal and one vertical outer surface, filled partially by the structural girder of nonmetallic material along its side under the effect of compressive forces. This offers an anchoring possibility for the force application points, as well as safety against buckling. Furthermore, the nonmetallic structural girder can also be provided according to the invention with mounting means serving for the reception of supply lines arranged in the interior of the total profile construction, which lines could otherwise come into harmful mutual contact or could damage the profile wall, such as, for example, raw wire lines for power current.
A further feature of preferred embodiments of this invention provides that the profile member of metal has at least one closed hollow space arranged at least partially in the zone under compressive stress, this hollow space being entirely filled with a nonmetallic material. This makes it possible to introduce, after the assembly of the hollow bending beams, a nonmetallic material which can be pumped subsequently into the hollow space. This reduces the costs of transportation and assembly. Another embodiment of the present invention provides that the profile member of metal is a steel profile in the form of a double-T-girder with a box disposed on the top chord. The box can be formed by a mass-produced U-shaped profile member according to the invention. However, not only series-produced profile members are employed; rather, the attached box forms a track element affording the convenient mounting of rails and distributing all introduced forces absorbed by the double-T-girder.
A preferred embodiment of the present invention which is an alternative of the above-mentioned constructions provides that the steel profile consists of two pipes, one inserted in the other, the walls of which pipes are in contact with each other along a straight line. This arrangement makes it possible, with a given external diameter and with the use of pipes, to surround an internal chamber with an external chamber in the matter of a reinforcing bracket, wherein the internal chamber can serve for the reception of supply lines or cargo, while the outer chamber is filled with a nonmetallic material, offering a rigidifying resistance against bending forces, as well as lateral forces and torsional forces. In accordance with a further development of the invention, the contact zone is located on the side of the pipes facing away from the primary bending forces. The zone of the largest thickness of the nonmetallic profile is disposed exactly in the zone of the compressive forces, whereas the zone of the largest thickness of the metallic profile is arranged in the zone of the tensile forces.
In another arrangement according to the invention, the total profile has a longitudinal slot in the contact zone of the two pipes. This makes it possible to insert or withdraw without difficulties supply lines subsequently into or from the interior of the profile; if the width of the slot is adequate, connection and repair operations can likewise be carried out.
In a further embodiment, both pipes are connected outside of the contact zone, preferably by clamping bolts, wherein the connecting elements (clamping bolts) pass through the nonmetallic profile material. This measure makes it possible to introduce the bending force into the bending beam not only on its topside but also on its bottom side. In this connection, the connecting members prevent that one of the pipes is lifted from the surface of the nonmetallic profile, or that the entire crescent-shaped profile is bent apart with its tips.
Another embodiment of the present invention resides in that profiles or wires for the mounting of wheels and/or current collectors, especially for suspension cars (compartments, cabins) are arranged in the interior of the inner pipe, particularly on one or both sides of the longitudinal slot in close proximity of the contact zone of the two pipes. The wheel suspensions are guided through the longitudinal slot of the profile. The track guidance is advantageous due to the fact that the current wires are accommodated without contact and safe from atmospheric influences and also satisfies requirements for environmental protection, since the rolling noises of the wheels are extensively damped by the sound-attenuating nonmetallic profile. Furthermore, such a profile prevents a derailed train from falling.
A further development of this invention consists in that the nonmetallic profile girder is seamlessly incorporated into the hollow space of the metallic profile and is made up of bulk material which, on the one hand, is capable of being pumped or poured and, on the other hand, has the behavior of a solid, rather than a liquid after compacting, i.e. it absorbs compressive forces and transmits same directionally. This avoids the difficulty encountered when a large-volume material undergoes a setting process, with a perhaps unduly high extent of shrinkage.
The invention furthermore relates to a process for the production of a bending beam according to this invention by a composite steel-concrete cast wherein, during the setting of the concrete, the steel and/or the concrete are tempered (temperature-controlled) so that the finished cast article is free of tension, under consideration of the shrinkage dimensions. Since concrete heats up during setting, an undesired stress condition results during composite casting after cooling of the concrete; this can be prevented in accordance with the process of this invention.
One embodiment of the process resides in that the steel profile is heated. Heating during the relatively short setting period is sufficient. The good heat conductivity of steel is a contributing factor in the reduction of stress formation by nonuniform heating.
If the concrete profile is very simple, as contrasted to the steel profile, or if a coating does not permit the heating of the steel, an alternative embodiment of this invention provides that the setting concrete is being cooled.
Another development of the process of this invention relates to the aspect of incorporating cooling ducts into the concrete for cooling purposes. In this connection, the cooling duct dimensions can be adapted to the shape of the profile. The cooling ducts can be used, after the cast article has been completed, as supply or conveying lines.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.